Digital inter-pupillary distance adjustment

ABSTRACT

Stereoscopic viewing systems may be adjusted for a user&#39;s inter-pupillary distance (IPD). An inter-pupillary distance (IPD) value is determined from a signal from a position sensitive device coupled to two moveable sighting fixtures mounted to a head mounted display (HMD) having two fixed optics configured for a specific inter-pupillary distance. The position sensitive device is configured to produce a signal that corresponds to a distance between the two sighting fixtures. The images are warped with a processor to optimize display of the images with the two fixed optics for the determined IPD value.

CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.15/461,225, filed Mar. 16, 2017, the entire disclosures of which areincorporated herein by reference. U.S. patent application Ser. No.15/461,225 is a continuation of U.S. patent application Ser. No.14/187,127, filed Feb. 21, 2014, the entire disclosures of which areincorporated herein by reference. U.S. patent application Ser. No.14/187,127 claims the priority benefit of U.S. Provisional PatentApplication No. 61/779,272, filed Mar. 13, 2013, the entire disclosuresof which are incorporated herein by reference.

FIELD OF THE DISCLOSURE

Aspects of the present disclosure relate to stereoscopic 3D images anddigital image adjustment.

BACKGROUND OF THE DISCLOSURE

Head mounted displays (HMDs) and stereoscopic viewing devices (SVDs)have two lenses or apertures that a user can look into to seestereoscopic 3D images. Typically, such systems utilize or generateseparate virtual images for the left and right eye. These images areprojected toward the user's left and right eyes through separate optics.

People have different distances between their eyes (inter-pupillarydistance or IPD). The IPD for adults can range from about 50 millimetersto about 70 millimeters, which is a significant range of variation. Totake this variation into account, adjustment of the HMD or SVD isrequired due to aberrations or stereo separation.

Aberrations include (but are not limited to) Geometric Lens distortion(the lens curves straight lines), transverse/lateral ChromaticAberration (optics focus different wavelengths of light at differentpositions on the focal plane), Coma (a variation in magnification awayfrom the center of the optic) and vignetting (image brightness changesfrom the center of the image). Stereo separation refers to the distancebetween each virtual image along the axis between two virtual camerasrepresenting the human eyes.

To take these IPD-related effects into account, a HMD or SVD must haveoptics that can physically adjust to the spacing of the user's eyes orthe content being shown on the system needs to be adjusted.

With a HMD/SVD that contains fixed optics (i.e., optics having a stereoseparation distance that is fixed mechanically to a specific IPDdistance), content will only look correct (e.g., reduced aberrations andcorrect 3D depth perception) if the user's IPD matches the IPD specifiedby the system's optical design (a HMD/SVD can be optically designed todeliver correct images to one specific IPD that can be different to themechanical IPD of optics in the device). Therefore in a fixed opticsystem, to correctly display high quality images to users with varyingIPDs that system must adjust the content that is displayed dynamically.

It is possible to correct the content being shown in software and/orhardware if the user's IPD is known. Hardware (cameras, infraredsensors, etc.) exist to measure the user's IPD, but these can addsignificant cost, complexity and additional power requirements to asystem.

It is within this context that aspects of the present disclosure arise.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 is schematic diagram of a user viewing an image on a displaydevice that displays stereoscopic images.

FIG. 2A is a simulated image of a graph paper through a center portionof lens.

FIG. 2B is a magnification of the central part of the image in FIG. 2A.

FIG. 2C is a simulated image of a graph paper through a point 2.5 mmleft of center.

FIG. 2D is a magnification of the central part of the image in FIG. 2C.

FIGS. 3A-3B depict an example of a calibration sequence to illustratevarious aspects of the present disclosure.

FIG. 4 is a schematic diagram depicting a low-cost hardware device forIPD adjustment according to various aspects of the present disclosure.

FIG. 5 is a schematic diagram of a system for performing IPD adjustmentaccording to various aspects of the present disclosure.

FIG. 6 is a diagram describing the instructions for executing anoperation for IPD adjustment according to various aspects of the presentdisclosure.

DETAILED DESCRIPTION

Although the following detailed description contains many specificdetails for the purposes of illustration, anyone of ordinary skill inthe art will appreciate that many variations and alterations to thefollowing details are within the scope of the invention. Accordingly,the exemplary embodiments of the invention described below are set forthwithout any loss of generality to, and without imposing limitationsupon, the claimed invention.

Aspects of the present disclosure include a simple “Digital IPDAdjustment” that enable a user to digitally adjust the content beingdisplayed to match the user's IPD. This adjustment can be implemented ineither software or hardware or some combination of software andhardware.

Aspects of the present disclosure include adjusting the content withsoftware that acts on digital image content, but not as part of theoriginal content creation process, however the software may also selectpre-generated content for each adjustment.

Hardware may be used to apply an adjustment to a content video signalprior to it being displayed to the user through the optics.

The user can initiate the adjustment through suitably configuredhardware, e.g., by buttons, sliders, dials, etc. on or near the HMD/SVD.Alternatively, the adjustment may initiated by the user throughsoftware, e.g., by in-content menus or by a specific calibrationprocess.

The calibration process may be implemented using a simple calibrationscreen that is displayed once the user presses the mentioned buttons,and the user can align colored objects until their color appears correctto the user prior to proper usage. Different forms of optical distortioncorrection can be applied based on the user's digital IPD selection, anda correct image can be shown to the user.

Once the adjustment is selected by the user, the above aberrationsand/or stereo separation may be changed dynamically at an interactiverate such the user can see the effect of the adjustment within a shortperiod of time. The user can then adjust the imaging of the HMD/SVDuntil the content looks correct to the user.

In addition, once the user has adjusted the HMD/SVD image quality tomatch their IPD, this adjustment (Digital IPD value) can be stored onthe HMD/SVD or device connected to the HMD/SVD to be matched to theuser. Therefore every time the user wears the HMD/SVD the content isadjusted to display correct for them and they no longer need tore-adjust.

An example of such user matching could include storing the “Digital IPD”value of the user in their profile/login on a computer or gaming system.Every time that user logs into their computer or gaming system, theirIPD value is retrieved and the content on the HMD/SVD is adjusted forthem.

Aspects of the present disclosure can include a calibration sequencethat is integrated into other content, such as a game, to enhance theuser experience and provide for more seamless operation and even performthe calibration without the user being aware that calibration is takingplace.

Aspects of the present disclosure can include further optimization of anIPD calibration sequence by integrating the calibration sequence intocontent, such as, e.g., video content or game content rather thanproviding for a dedicated calibration sequence.

The problem of optical distortion due to eye shift (the human eye beingshifted horizontally from the center axis of the optic) is depicted inFIG. 1. A user 105 looks into display device 110 to view a stereoscopicimage. A processing system 106 sends a stereoscopic image to displaydevice 110, which contain optics 115 corresponding to each of a user'seyes. However, in FIG. 1, the IPD of the user does not match up with theoptics of the display device, resulting in aberrations perceived by theuser.

The problem of optical distortion due to eye shift (the human eye beingshifted horizontally from the center axis of the optic) is furtherexemplified in FIGS. 2A and 2B vs. FIGS. 2C vs. 2D. In these picturesyou can see the geometric and chromatic aberration changes as the eyeshifts from center to 2.5 mm to the left. The center image of FIGS. 2Aand 2B was generated for an IPD of 63.5 mm and the image of FIGS. 2C and2D show a 2.5 mm shift (a user with an IPD of 68.5 mm). The user with68.5 mm IPD will get a slightly different image than the user with 63.5mm. Chromatic aberration in the image of FIG. 2D may be exhibited in theform of fringing of colors in the centerline. This can be seen as ablurring of the vertical centerline in FIG. 2D compared to therelatively sharper centerline in FIG. 2B. It is noted that the originalimages were in color and the color fringing is exhibited as the blurringseen in the black and white images.

Through software warping, FIGS. 2C and 2D can be changed to appear thesame as FIGS. 2A and 2B to a user with 68.5 mm IPD. There are variousmethods of software image warping and the present disclosure will notcover those in detail, however a simple example would be the following:

For a simple spherical image warp with linear correction of TCA(Transverse Chromatic Aberration):

R2=TX*TX+TY*TY

DX=TX+(TX*R2*K)

DY=TY+(TY*R2*K)

RX=(DX*K2)+K3

RY=(DY*K2)

GX=(DX*K4)+K5

GY=DY*K4

BX=(DX*K6)+K7

BY=DY*K6

TX,TY are input image coordinates

K is the amount spherical distortion

K2 is the amount of linear Red Transverse Chromatic Aberration

K3 is the amount Red Chromatic linear shift due to IPD

K4 is the amount of linear Green Transverse Chromatic Aberration

K5 is the amount Green chromatic linear shift due to IPD

K6 is the amount of linear Blue Transverse Chromatic Aberration

K7 is the amount Blue chromatic linear shift due to IPD

RX,RY is the output red image coordinates

GX,GY is the output green image coordinates

BX,BY is the output blue image coordinates

In the above simple example, variables K3, K5, K7 are based on a user'sIPD.

For example:

K3=IPD in mm*0.5*Eye(−1 for Left or 1 for Right)*(Image width inpixels/Display width in mm)

Using the examples above, the user can adjust the IPD value until thedistorted image appears correct to them.

The calibration process may be based on a variation of IPD-dependentsettings, such as stereo separation or chromatic adjustment (e.g.,chromatic linear shift), until the image appears normal. By way ofexample and not by way of limitation, a calibration image can include asimple line or grid pattern. The calibration image may be generated insoftware or may be an image created by a graphic designer. The stereoseparation of two such images can be changed in software and a series ofsuch images can be briefly presented by the display device. Each stereoseparation value can be correlated to a corresponding IPD. Thestereoscopic image distance may initially be set to an extreme value sothat the user sees two images. The system can prompt the user to enteran input when the two images appear to fuse into a single image (e.g.stereo matching). The system can then set the IPD value for presentationof subsequent images to the IPD value that corresponds to the stereoseparation when the user saw the images fuse.

The input from the user may be in any suitable form, e.g., press abutton, click on an icon, a voice command, depending on the nature ofthe system that is used in conjunction with the display. By way ofexample, and not by way of limitation, if the display is used inconjunction with a video game console, the command may be enteredthrough a button, joystick, or other control on a game controller.

By way of further non-limiting example, one user input could set theIPD-dependent image setting value and a second input could indicate thatthe image appears correct. The input that sets the value or indicatesthat the image appears correct may be in the form of, e.g., pressing anUp/Down button on the HMD/SVD or attached device (e.g., controller),moving a Slider on the HMD/SVD or attached device, rotating a dial onthe HMD/SVD or attached device, adjusting a user interface (UI)component (virtual slider, buttons, etc.) in the content presented bythe display.

The IPD selection may be quantized in discrete steps or may be analog.The process could be either in a special calibration sequence or withinthe content itself (e.g., within game title for video gameimplementations). The hardware/software performing the opticaldistortion correction could store pre-generated data per discrete IPDvalue and interpolate between to account for precise IPD adjustment.

To optimize the calibration process, the calibration screen image may beconfigured to take advantage of key features of human vision andstereoscopic display systems. First, the aberrations and effects ofstereoscopic image distance tend to be most pronounced near the edges ofthe images. Second, visual acuity tends to be highest at the center ofthe field of vision. Since the aberrations are greatest near the edgesof the image it is desirable to place noticeable parts of the patternnear the edges of the image. Placing the noticeable parts of thepattern, e.g., particularly dark or thick lines, near the edges of theimage, particularly the left and/or right edges, may also draw theuser's attention to the edges of the image and cause the user's eyes torotate to focus on the edge of the image. Accordingly, the calibrationsequence can be optimized to provide more accurate coincidence of thesystems IPD display settings with the particular user's IPD.

By way of example and not by way of limitation, this can be accomplishedusing a calibration sequence that is implemented by prompting a user tofocus on a left or right portion of the screen, or by otherwise drawinga user's eyes to focus on an aspect of the calibration image that islocated on the edge or periphery of the displayed calibration image. Byway of example, this can be accomplished by using a calibration imagehaving substantially all of its noticeable image aspects located onperipheral portions of the displayed image, or by particularlyemphasizing image aspects that are located on peripheral portions of theimage (e.g., on extreme left or right portions).

By way of example and not by way of limitation, the calibration imagecan include a set of colored rings whose circumferential edges arelocated on the periphery of the displayed calibration image, therebydrawing the user's attention to focus on the border of the rings. Anexample of such a calibration image sequence is depicted in FIGS. 3A-3B,which include particularly exaggerated and simplified aspects forpurposes of illustration. Calibration image 300 includes a ringdisplayed stereoscopically to a user on a display device. In FIG. 3A,due to chromatic aberrations caused by the system's IPD not matching theuser's IPD, the ring of the calibration image is initially perceived bythe user as separated colored rings 305 a, 305 b, and 305 c. Thecalibration sequence includes adjustment of one or more IPD-dependentdisplay settings of the calibration image 300 in accordance with aspectsmentioned herein, until it is perceived by the user as a single whitering 310 as depicted in FIG. 3B.

Accordingly, the user's attention is focused on the peripheral portionsof the calibration image because particularly noticeable aspects of thecalibration image, or even the only noticeable aspects of thecalibration image (i.e., in this case, the border of the ring) isdisplayed on the peripheral portions of the calibration image. Thisdraws the user's center of vision to the edges of the calibration image,focusing the user's center of vision, where visual acuity is thegreatest, on the portions of the calibration image where IPD dependentaberrations are most pronounced. Furthermore, by using a calibrationimage that emphasizes aspects of the calibration image that are locatedon the edges or peripheral portions of the field of view, the user'scenter of vision can be drawn to those desired portions of thecalibration image without a specific prompt (e.g. without explicitlytelling the user to look to the right or left), providing for moreseamless operation and enhancing the user experience.

By way of further example, the rings 305 a, 305 b, 305 c can furtherinclude image aspects located in their centers, such as pronouncedvertical and horizontal lines extending through their centers, to enablethe user to first match up calibration images that include greatlyexaggerated aberrations that are easily noticeable in the center of thecalibration image, thereby providing an approximately optimized IPDdependent display setting, then enabling the user to fine tune thecalibration by matching up the circumferential circular portions on theperiphery of the image so that their color is perceived white, therebyproviding more accurate IPD optimization of the display settings.

It is noted that the rings of FIGS. 3A-3B are but one example providedto illustrate various aspects of the present disclosure. Numerous othercalibration images and sequences can be used consistent with the presentdisclosure, including but not limited to, triangles, squares, grids,lines, pictures and videos of objects, animals, people, etc.

Aspects of the present disclosure can be further extended to usinghardware to determine the user's IPD automatically, or provide a roughapproximation of the user's IPD that the user can further fine tune, orotherwise correct if inaccurate. This allows the possibility of usinglow cost hardware to gather an approximate measurement of the user's IPDthat would be correct for the largest percentile of users, but stillallow users to adjust more precisely if required.

An example of a low cost hardware solution is depicted in FIG. 4, whichdepicts display device 400 that includes a set of spectacles with a pairof rings or other sight fixtures 405 a, 405 b. The sight fixtures 405 a,405 b are slidable or otherwise mounted to the spectacles in a mannerthat enables them to slide or to laterally or otherwise move theirposition with respect to each other.

The sighting fixtures 405 a, 405 b could be mounted to a positionsensitive device 410, e.g., a rheostat, that is calibrated to provide asignal proportional to the distance between sighting fixtures 405 a andsighting fixture 405 b. The user wears the device and adjusts thesighting fixtures 405 a, 405 b until each fixture is centered on acorresponding one of the user's eyes. The signal from the device canthen be fed to a computer or other device including a processing system415 that reads the IPD from the spacing between the sighting fixtures405. IPD setting corresponding to the user can then be furtherfine-tuned digitally in conjunction with aspects of the presentdisclosure, if desired.

In some aspects, sighting fixtures 405 can be adjusted by way of aphysical slider, knobs, buttons, touchscreen, etc. located on the device400 or other part of the system which enable the user to physicallyadjust the location of the sighting fixtures to correspond to the user'seyes. In some aspects, the sighting fixtures may be adjusted by way ofcomponents already existing in the system, including but not limited tobutton presses on a game controller or remote control, keyboard strokes,mouse movements, etc. In some aspects, software from the processingsystem remaps functions of those existing control components uponinitialization of a calibration sequence to correspond to adjustment ofthe sighting fixtures 405, and wherein the display device 400 furtherinclude an electric motor or other mechanism to electronically controlthe position of the sighting fixtures 405 relative to one another basedon inputs received from the user. The device 400 can be incorporatedinto an HMD or SVD, or may be a separate standalone device. In theexample illustrated in FIG. 4, the device 400 is incorporated into astereo display 406 having fixed optics.

Because the greatest variation in IPD is a result of different user faceshapes having eyes that are closer or further together, adjustability ofsighting fixtures can be limited to relative adjustment in thehorizontal direction to keep costs down. However, aspects of the presentdisclosure further include low cost hardware display device solutionsthat enable vertical adjustments of the sighting fixtures or otherpositional adjustments in addition to simply horizontal adjustment toprovide even further adjustability for different face shapes and pupilpositions of a user and enable increased comfort to a user looking intoa stereoscopic display.

Aspects of the present disclosure include systems configured toimplement digital IPD adjustment of the various types described above.By way of example, and not by way of limitation, FIG. 5 illustrates ablock diagram of a computer system 500 that may be used to implement IPDadjustment according to aspects of the present disclosure. The system500 generally may include a main processor module 501, a memory 502, adisplay 516, and a user interface 518. The processor module 501 mayinclude one or more processor cores, e.g., single core, dual core, quadcore, processor-coprocessor, Cell processor, architectures, and thelike.

The memory 502 may be in the form of an integrated circuit, e.g., RAM,DRAM, ROM, and the like. The memory may also be a main memory that isaccessible by all of the processor cores in the processor module 501. Insome embodiments, the processor module 501 may have local memoriesassociated with one or more processor cores or one or moreco-processors. An IPD adjustment program 503 may be stored in the mainmemory 502 in the form of processor readable instructions that can beexecuted by the processor module 501. The IPD program 503 may beconfigured enable digital IPD adjustment of an image to be displayed ondisplay device 516, in accordance with various aspects of the presentdisclosure. The IPD adjustment program 503 may be written in anysuitable processor readable language, e.g., C, C++, JAVA, Assembly,MATLAB, FORTRAN and a number of other languages.

Input or output data 507 may be stored in memory 502. During executionof the IPD adjustment program 503, portions of program code and/or data507 may be loaded into the memory 502 or the local stores of processorcores for processing the processor 501. By way of example, and not byway of limitation, the input data 507 may include data corresponding toa signal received by a user indicating optimal IPD dependent displaysettings or data corresponding to and adjustment signal by a user foradjusting a calibration image, wherein the data 507 is received fromuser interface 518.

The system 500 may also include well-known support functions 510, suchas input/output (I/O) elements 511, power supplies (P/S) 512, a clock(CLK) 513 and cache 514. The apparatus 500 may optionally include a massstorage device 515 such as a disk drive, CD-ROM drive, tape drive, orthe like to store programs and/or data.

The device 500 may also include a display unit 516 and user interfaceunit 518 to facilitate interaction between the apparatus 500 and a user.The display unit 516 may be in the form of an HMD or SVD that displaystext, numerals, graphical symbols or images. The user interface 518 mayinclude a keyboard, mouse, joystick, light pen, or other device that maybe used in conjunction with a graphical user interface (GUI). Thedisplay unit 516 and user interface unit 518 may also optionally beintegrated into a single unit, such as, e.g., by way of sliders,buttons, or other controls provided on a SVD or HMD. The apparatus 500may also include a network interface 520 to enable the device tocommunicate with other devices over a network 522, such as the internet.The system 500 may receive one or more frames of streaming data (e.g.,one or more encoded image frames) from other devices connected to thenetwork 522 via the network interface 520. These components may beimplemented in hardware, software, or firmware, or some combination oftwo or more of these.

A method for digital IPD adjustment in accordance with various aspectsof the present disclosure is depicted in FIG. 6. The method 600 can beused for adjustment of a stereoscopic image to optimize viewing for aparticular user's IPD. The method 600 includes displaying a calibrationimage 605 on a display device having stereoscopic viewing capabilities.The method 600 further includes adjusting one or more IPD-dependentdisplay settings of the calibration image 610. Method further includesreceiving an input from the user 615 corresponding to the one or moreIPD-dependent display settings being optimized for the particular IPD ofthe user. The method 600 further includes storing the one or moreoptimized IPD dependent display settings 620. Method 600 furtherincludes digitally altering a subsequently displayed image 625 tooptimize the subsequently displayed image for the user's IPD based onthe stored display setting.

The method 600 can be executed by a computer or other processing system,wherein the one or more stored IPD dependent display settings are usedto optimize a subsequent viewing experience on a display device for auser.

The method 600 can further include various aspects according to thepresent disclosure.

The method 600 can be implemented in program instructions embodied in anon-transitory computer readable medium and executable by a system forIPD adjustment, according to various aspects of the present disclosure.

Aspects of the present disclosure provide for a relatively inexpensiveand simple adjustment of stereoscopic viewing devices or head mounteddisplays to take into account differences in users' inter-pupillarydistance. Modification of the display or viewing device is not required.This allows for adjustment of displays with fixed viewing optics.

While the above is a complete description of the preferred embodiment ofthe present invention, it is possible to use various alternatives,modifications and equivalents. Therefore, the scope of the presentinvention should be determined not with reference to the abovedescription but should, instead, be determined with reference to theappended claims, along with their full scope of equivalents. Any featuredescribed herein, whether preferred or not, may be combined with anyother feature described herein, whether preferred or not. In the claimsthat follow, the indefinite article “A”, or “An” refers to a quantity ofone or more of the item following the article, except where expresslystated otherwise. The appended claims are not to be interpreted asincluding means-plus-function limitations, unless such a limitation isexplicitly recited in a given claim using the phrase “means for.”

What is claimed is:
 1. A method, comprising: determining aninter-pupillary distance (IPD) value with a processor from a signal froma position sensitive device coupled to two moveable sighting fixturesmounted to a head mounted display (HMD) having two fixed opticsconfigured for a specific inter-pupillary distance, the positionsensitive device being configured to produce a signal that correspondsto a distance between the two sighting fixtures; and warping images withthe processor to optimize display of the images with the two fixedoptics for the determined IPD value.
 2. The method of claim 1, whereinwarping the images includes correcting the images for one or moreaberrations.
 3. The method of claim 1, wherein the aberrations includegeometric lens distortion, chromatic aberration, coma, vignetting or acombination thereof.
 4. The method of claim 1, further comprisingstoring the setting of IPD for the user in digital memory.
 5. The methodof claim 4, further comprising automatically adjusting images presentedon the display using the stored setting of IPD for the user.
 6. Anapparatus, comprising: a computer processing system configured, bysuitable programming, to perform a method comprising: determining aninter-pupillary distance (IPD) value from a signal from a positionsensitive device coupled to two moveable sighting fixtures mounted to ahead mounted display (HMD) having two fixed optics configured for aspecific inter-pupillary distance, the position sensitive device beingconfigured to produce a signal that corresponds to a distance betweenthe two sighting fixtures; and warping images with the computerprocessing system to optimize display of the images with the two fixedoptics for the determined IPD value.
 7. The apparatus of claim 6,wherein warping the images includes correcting the images for one ormore aberrations.
 8. The apparatus of claim 6, wherein the aberrationsinclude geometric lens distortion, chromatic aberration, coma,vignetting or a combination thereof.
 9. The apparatus of claim 6,wherein the method further comprises storing the setting of IPD for theuser in digital memory.
 10. The apparatus of claim 9, wherein the methodfurther comprises automatically adjusting images presented on thedisplay using the stored setting of IPD for the user.
 11. The apparatusof claim 6, further comprising the head mounted display HMD having twofixed optics configured for a specific inter-pupillary distance.
 12. Theapparatus of claim 6, further comprising the position sensitive devicecoupled to two moveable sighting fixtures.
 13. The apparatus of claim 6,further comprising the position sensitive device coupled to two moveablesighting fixtures and the head mounted display (HMD) having two fixedoptics configured for a specific inter-pupillary distance.
 14. Anon-transitory computer readable medium containing program instructionsfor inter-pupillary distance (IPD) adjustment on a display devicecomprising fixed optics, wherein execution of the program instructionsby one or more processors of a processing system causes the one or moreprocessors to carry out an IPD adjustment method, the IPD adjustmentmethod comprising determining an inter-pupillary distance (IPD) valuefrom a signal from a position sensitive device coupled to two moveablesighting fixtures mounted to a head mounted display (HMD) having twofixed optics configured for a specific inter-pupillary distance, theposition sensitive device being configured to produce a signal thatcorresponds to a distance between the two sighting fixtures; and warpingimages with the processing system to optimize display of the images withthe two fixed optics for the determined IPD value.
 15. Thenon-transitory computer readable medium of claim 14, wherein warping theimages includes correcting the images for one or more aberrations. 16.The non-transitory computer readable medium of claim 14, wherein theaberrations include geometric lens distortion, chromatic aberration,coma, vignetting or a combination thereof.
 17. The non-transitorycomputer readable medium of claim 14, wherein the IPD adjustment methodfurther comprises storing the setting of IPD for the user in digitalmemory.
 18. The non-transitory computer readable medium of claim 17,wherein the IPD adjustment method further comprises automaticallyadjusting images presented on the display using the stored setting ofIPD for the user.